Look on the instructions for Drive Image 7. It highly recommends that you do a test by booting up your computer via the DI CD to check that the setup works OK. If it doesn't (?!?!?!) you're in schtuck - which is the reason for doing the test run, of course.
There are ways of getting going by other methods which the DI 7 manual explains.
Assuming a catastrophic software failure and Windows doesn't boot up but DI will, it is a matter of less than an hour to get everything as it was at the time of your last backup. In the case of a hardware failure it will take longer as you have to identify the failed component first.